1. Field of the Invention
The present invention relates to a rechargeable battery, and more particularly, to an improvement of the temperature detection portion in a sealed rechargeable battery wherein elements for electromotive force are accommodated in a sealed battery case.
2. Description of Related Art
For the temperature detection mechanism in sealed rechargeable batteries, which are used, for example, in electric vehicles, an embedded-type structure is known, wherein a temperature sensing element is integrally provided in the battery case. In order to detect the internal temperature of the battery while keeping the inside thereof airtight, a temperature detection hole having a bottom is formed in the battery case, which is sealed against the inside of the battery case and open to the outside, and a temperature sensor element is inserted into this temperature detection hole, which is then filled with a synthetic resin to integrate it into one piece with the battery case.
In Japanese Published Unexamined Patent Application No. 9-120846, a configuration is disclosed, in which a temperature sensor is inserted into a temperature detection hole having a bottom, as described above, and bonded or welded with an adhesive or a resin, or fixed by other means, so that the temperature inside the battery can be detected from outside the battery.
However, in such embedded-type temperature detection mechanism, there is the danger that the precision and the responsiveness of the temperature sensing element deteriorates depending on how it is mounted in the battery case. Moreover, it is difficult to determine whether the arrangement of the temperature sensing element is appropriate. For the purpose of embedding the temperature sensor in the hole, the manufacturing process of the battery case is relatively complicated, with the result that costs become high and handling is not easy. Moreover, there is the problem that maintenance is not easy, since it is necessary to exchange also the temperature sensor as well as the wiring when batteries are to be exchanged.
In the configuration disclosed in the above mentioned publication, a separate temperature sensor is inserted into a temperature detection hole having a bottom in the battery case. However, this publication does not particularly show a means for inserting the temperature sensor in the temperature detection hole without creating a gap with the walls of the temperature detection hole, and it is not clear whether it is actually possible to perform temperature detection with high precision and responsiveness.
In view of these problems of the prior art, it is an object of the present invention to provide a rechargeable battery, in which the temperature of the elements for electromotive force in a sealed battery case can be detected with high precision and responsiveness, and which has good operability with regard to assembly and maintenance.
To achieve the above object, the present invention provides a rechargeable battery, comprising: a battery case for accommodating therein elements for electromotive force in a sealed condition; a temperature detection hole which is defined by a cylindrical cavity having a bottom formed in the battery case; a temperature sensor mounted in the temperature detection hole, having a sensing end at a lower end thereof; and a mounting means for mounting the temperature sensor removably in the temperature detection hole such that the sensing end at the lower end of the temperature sensor is tightly pressed against the bottom of the temperature detection hole. Since the temperature inside the battery is detected through the bottom wall of the temperature detection hole while the inside of the battery case remains tightly sealed, and since the sensing end of the temperature sensor is pressed against the bottom wall of the temperature detection hole, the battery temperature can be detected with high precision and responsiveness. Moreover, since the temperature sensor can be removed from the temperature detection hole of the battery case, the operability when attaching the temperature sensor and when replacing the batteries for maintenance is good.
Specifically, an engaging hook is provided at an edge portion of the temperature detection hole in the battery case, while an engaging flange that is elastically deformable is formed on the temperature sensor, so that, when the temperature sensor is mounted in the temperature detection hole, the elastic restorative force of the engaging flange that is engaged in elastic deformation with the engaging hook exerts pressure on the temperature sensor. Thus the temperature sensor can be mounted with one-touch operation. In addition, the elastic restorative force of the engaging flange presses the sensing end of the temperature sensor securely against the bottom wall of the temperature detection hole.
The temperature detection hole and the temperature sensor respectively have small-diameter portions at their lower ends, so that heat is conducted to the sensing end of the temperature sensor not only from the bottom wall of the temperature detection hole, but also from the vicinity thereof, which enables temperature detection with even higher precision and responsiveness, because the thermal capacity of the temperature detection portion is small.
The temperature sensor comprises a cylindrical sensor case having a bottom wall, and a sensing element inserted into the sensor case such as to contact the bottom wall of the sensor case, the interior of the sensor case being filled with a resin. Thanks to the construction wherein the sensing element is arranged inside the sensor case and formed in one piece with the sensor case, there is no danger that the leads break off the sensing element, whereby handling is made easier, and temperature detection with high responsiveness and smooth thermal conduction becomes possible. The responsiveness of the temperature sensor can be further improved by making the bottom wall of the sensor case thinner.
Alternatively, the temperature sensor comprises a cylindrical sensor case without a bottom, and a sensing element inserted into the sensor case such as to extend through the sensor case, the interior of the sensor case being filled with a resin. Thanks to the construction wherein the perimeter of the sensing element is protected by the sensor case and the filling resin, and that the sensing element is formed in one piece with the sensor case, there is no danger that the leads break off the sensing element, whereby handling is made easier. This also enables temperature detection with even higher responsiveness, because heat is conducted directly from the bottom wall of the temperature detection hole to the sensing element.
The temperature sensor is further provided with a wire-holding hook for holding the wires, so that stress concentrations in the wires in a direction in which they are pulled out of the temperature sensor, which may cause wire rupture, can be prevented, even when an external force is accidentally applied to the wires.
The engaging hook is elastically deformable in a direction that is perpendicular to an axis direction of the temperature detection hole, and the temperature sensor comprises a protrusion that restricts displacement of the engaging hook, so that excessive deformation that may cause breaking of the engaging hooks when mounting or removing the temperature sensor can be prevented.
The temperature detection hole of the battery case, the sensor case of the temperature sensor and the mounting means are all made of synthetic resin, so that heat is not dispersed to the outside, thereby making appropriate temperature detection possible.
The temperature detection hole of the battery case is arranged such that its bottom wall is in contact with or in close proximity to a maximum temperature location of the elements for electromotive force, for example, at an upper central portion of the elements for electromotive force or near the collectors, where the temperature is the highest and heat is dissipated the slowest, whereby the temperature of the battery can be detected with high responsiveness.
While novel features of the invention are set forth in the preceding, the invention, both as to organization and content, can be further understood and appreciated, along with other objects and features thereof, from the following detailed description and examples when taken in conjunction with the attached drawings.